Recently, wireless LAN technologies, such as IEEE 802.11 or ETSI Hiperlan 2, have been developed that may be used in conjunction with existing networks, including mobile networks, i.e., 3G or 2G, to provide new high speed services, for example video streaming. The wireless LAN services provide the advantages of faster data speeds, generally on the order of about ten times faster than those provided by a 3G network, but are much more limited in the area of coverage and the number of users that can be connected to the base station. It is envisioned that a mobile terminal user would transition from a mobile telephony network to a wireless LAN upon entering a coverage area of the wireless LAN, and transition to the mobile telephony network upon leaving the coverage area of the wireless LAN.
A mobile network is essentially made up of a radio access network and a core network. A mobile terminal has a relationship with the core network through the radio access network. That is, a mobile terminal needs to be connected to the radio access network in order to communicate with the core network. The wireless LAN overlay uses a wireless LAN technology, such as ETSI Hiperlan 2 or IEEE 802.11, as the radio access network. The wireless LAN technology is generally more powerful than the mobile radio access network with regards to the available bandwidth. The wireless LAN is generally intended to cover a hot spot area, for example, an airport, where the number of potential users may be important. An issue faced in a system comprising a mobile network having one or more wireless LAN disposed therein is the management of the handoff as a mobile terminal moves between a 3G cell and a wireless LAN area.
Consider the case when a mobile terminal enters the coverage area of a wireless LAN that exists within the coverage area of a radio access network of a mobile network. The mobile terminal is currently attached to the radio access network. The wireless LAN may be detected using various detection methods known in the art. Once the wireless LAN has been detected, a handoff procedure must be performed to transition the mobile device from the access network of the mobile network to the wireless LAN. The handoff procedure may be complicated depending on the type of connection the mobile device has with the core network, i.e., circuit switching connection, a packet switching connection, or both. A good handoff procedure avoids data loss as much as possible during the switch between the two access networks. For the packet switching domain, it is possible, during handoff to buffer the packets. However, such buffering may introduce delay and does not guarantee zero loss of data. For the circuit switching domain, the process is more delicate due to the conversational nature of the connection that must be guaranteed. In any event, handing off the mobile terminal from one access network to another during an on going call may require the use of a complex and expensive protocol to ensure a seamless transfer.
Therefore, there is a need for a handoff strategy that does not require a complex and expensive protocol to implement and minimizes the potential for data loss.